Performance based services guarantees or Service Level Agreements (SLAs) have become an integral component of any network data service offer. To support network performance SLAs network service providers must deploy a monitoring infrastructure overlaid on the production network. Typically, the monitoring infrastructure consists of network collection devices (NCDs, also called “test probes”) and the associated control software. The NCDs generate test traffic along predefined network segments between designated network endpoints. The performance of this test traffic is used as a measure of the network performance. The control software manages operations of NCDs, collects test results from NCDs, aggregates test results and produces performance testing reports. FIG. 1A illustrates an exemplary monitoring infrastructure consisting of four NCDs 10 (i.e., NCD-1, NCD-2, NCD-3 and NCD-4) connected to a communication network 40 via network elements 30. The NCDs 10 are managed by the control software 20′ over the communication network 40. The NCDs 10 can be managed in-band via one communication network or out-of-band via dedicated, physically separate management networks. For illustration purposes, the network elements 30 in FIG. 1A are four routers (i.e., Router-1, Router-2, Router-3 and Router-4). The network elements 30 are fully connected to the monitored network and may be placed in any part of the network: edge, access, core, backbone. In practice, each NCD or test probe may be physically attached to or integrated with a network element.
Complex networks require complex monitoring architectures with increasing number of NCDs. This may cause much difficulty in traffic management, given the fact that the amount of traffic generated by NCDs in complex networks may amount to 3-5% of the network bandwidth. While this amount of traffic may not present a problem in the core or backbone networks, it may cause congestion on the low grade access links or in high-priority real time queues. Currently, in order to avoid traffic congestion in the monitored network, either the amount of generated test traffic or the number of network segments covered by tests has to be limited. In either case, however, the accuracy of measurements is compromised.
Another problem with current network performance management is called “test storms”. It refers to a condition where certain interfaces at times are flooded with large amount of test traffic while at other times these interfaces are idle. When many NCDs run traffic tests at random times without sufficient coordination, test storms are likely to occur. To avoid “test storms”, one solution is to schedule performance tests that are to be executed by NCDs. Under current test scheduling methods, however, the NCDs are only pair-wise synchronized and no network-wide coordination of performance tests is available. The pair-wise synchronization, as illustrated in FIG. 1B, requires pre-selection of an NCD pair 14 (NCD-1 and NCD-2) or 16 (NCD-3 and NCD-4) for defining a test connection or test path 12′. After all tests are performed along this test connection 12′, the control software 20′ selects another pair of NCDs for testing the connection in between. Under this approach, “test storms” may be avoided. However, the overall testing efficiency is compromised.
In light of the above, there exists a need for a precise control of the amount of traffic generated by the active network performance tests without limiting the overall number of tests, test frequency, or the number of test paths covered by tests. There is a further need to avoid “test storms” through the network-wide coordination of executing test sequences and individual tests among all the testing devices in the network.